Carbohydrazide curing agent for epoxide type resins



United States Patent fifice 3,014,009 CARBOHYDRAZIDE CURING AGENT FOR EPOXIDE TYPE RESINS Harold H. Levine, San Diego, Calif., assignor to Narmco Industries, Inc., San Diego, Calif., a corporation of California No Drawing. Filed July 20, 1959, Ser. No. 328,060 4 Claims. (Cl. 260--47) This invention relates generally to thermosetting epoxide resinous compositions, and relates especially to thermosetting epoxide resin compositions which remain uncured at near room temperature and which can be rapidly cured by means of a relatively mild cure cycle.

For the ultimate processor, the advantages of a preblended epoxide resin composition over a two component or two part system of resin and curing agent therefor, are many. (By a preblended resin composition, I mean a resin composition having a curing agent incorporated therein at some time prior to final curing of the composition.) The one component system eliminates mixing operations, and measuring operations, eliminates mixing equipment, and avoids possibilities of waste due to errors in measuring or errors due to lack of thoroughness in mixing, at the ultimate processing level, and is thus of great commercial importance.

Of those preblended epoxide resin compositions in the prior art, there are some which are stable at room temperature, but these usually require a relatively severe curing cycle. In frequent laminating, bonding, coating, etc. applications, however, the use of a severe curing cycle detrimentally affects the material to which the resin composition is applied. Thus the preblended epoxide systems are, in many instances, not of practical use, even though stable, because of their required relatively severe curing cycle.

Bearing in mind the foregoing facts, it is a major object of the present invention to provide a stable, preblended epoxide resin composition that can be completely cured by means of a curing cycle which is substantially less severe than is usually found necessary for stable preblended epoxide resin compositions of the prior art.

It is another major object of the present invention to provide a stable preblended epoxide resin composition which can be cured by means of a relatively mild curing cycle, the resulting cured product having physical properties at least comparable to stable preblended epoxy systems of the prior art, which require a more severe curing cycle.

Another object of the present invention is to provide a stable preblended epoxide resin system, which can be processed in a novel manner, by means of a relatively mild curing cycle, the cured system having very greatly improved physical properties and very highly increased resistance to certain chemicals.

These and other objects and advantages will become clearly understood by referring to the following description.

In general, my invention is directed to the preparation of stable preblended systems which are nevertheless capable of being completely cured at relatively low temperatures and/ or within relatively short times. Hitherto, these two very desirable characteristics seemed incompatible in a single epoxide resin system. More specifically, I have discovered that carbohydrazide.

when mixed with epoxide resins, provides resinous comshort periods of time, compared to the usual stable pre blended epoxide resinous compositions of the prior art.

The epoxide compositions of my invention react to produce cured products which are, in general, at least equal, in physical properties to other cured epoxy compositions. My compositions are suitable for use as adhesives, coatings, potting compounds, castings and laminates or reinforced products.

Further, the carbohydrazide-epoxide resinous systems when cured in a novel manner, as disclosed in detail in a co-pending application entitled Novel Epoxide Type Resin Compositions and Process for Making Same of Finn Claudi-Magnussen and myself (which is incorporated herein by reference), exhibit outstandingly improved physical properties with respect both to conventionally cured carbohydrazide-epoxide resinous systems, and other conventionally cured, normally stable pre blended epoxide systems.

As a specific example of the advantages of our novel epoxide system over stable preblended systems of the prior art, parts Epon 828 (a bisphenol-A type of epoxide resin manufactured by the Shell Chemical Corporation) and 12 parts of carbohydrazide were mixed in a suitable container, the mixture being stable at 40 F. The mixture was then applied to a metal part and heated to a temperature of 300 F. for 40 minutes. A complete cure of the mixture thereby resulted.

In contrast, a stable preblended epoxide system of the prior art, comprising 100 parts of Epon 828 and 25 parts isophthalic dihydrazide, was applied to a metal strip, and completely cured. The cure cycle required,

however, for complete curing, was 350 F for 60 minutes. The resulting physical properties of the two systems were generally excellent and comparable in value. However, the increase in severity of the curing cycle in the Epon 828-isophthalic dihydrazide system frequently causes the part to which the resin system is applied to be adversely affected. For example, in the process of bonding some metals, it is believed that certain adverse changes in grain structure of the metal may take place when subjected to temperatures much above 300 F. for a period of an hour or more. Therefore, my 40 F. stable resin composition, which is a'highly reactive system at300 F., is extremely useful in such applications.

The seeming inconsistency in having a preblended epoxide resin system, stable at about 40 F., yet highly reactive at about 300'F. or lower, is theoretically explainable in terms of the structure of the carbohydrazide. It is believed that carbohydrazide has the reactivity of a hydrazinyl radical, due to the presence of the NH NH- portion of the carbohydrazide molecule, and does not act as a hydrazidyl radical. This behavior, of course, could not be predicted. The hydrazinyl portion appears to have an appreciably higher reactivity with functional epoxide groups than does the hydrazide radical. Thus, when dihydra zide-epoxide resin systems are cured, substantially higher curing temperatures and/ or longer curing times are necessary-indicating that the reactivity of the dihydrazides is substantially less than that of the carbohydrazide.

in light of the dihydrazide-epoxideresin system, could i not be made since therole played by the constituent radicals in carbohydrazide is not definitely ascertainable,

Patented Dec. 19, 1961 and does not necessarily bear any chemical relationship to dihydrazide compounds. Thus, for example, the dihydrazides are all organic compounds-e.g. oxalyl dihydrazide or adipyldihydrazide, whereas carbohydrazide are produced by the reaction of polyhydric phenols with either polyfunctional halohydrins or polyepoxides or mixtures thereof to form complex reaction products containing terminal epoxide groups is normally classed as an inorganic compound. And, as 5 0 will be seen in detail hereafter, the diyhdrazides react significantly ditferently to the partial advancement process described in the aboveidentified coendin a lication of Finn Claudi-Magnussen and m yself t hag does Thehreactluan i has a ep 9 equlvalelflcy greai' t an y t e epoxy equlva ency re erence ls carboh drazlde, lndlcatln a am essential differences be- 10 er tween the dihydrazides aid carbohydrazide. m 9 the ewel'age number of CP XY groups con- The carbohydrazide epoxide resin preblended system talned 1n the average molecule of the react on productl. of my invention is found to be additionally extremely 3 f s gg g ggg g resms also contam hydroxy useful because, in addition to its stability and mild g polyepoxides mas, be Saturated or unsaturated curin c cle, it is found that rocessin" the carboh drazide-e poiide resin system acc c arding t; the teachin s in ahphanc cyclpahphailc aliomanc. or heterocychp and the aboveddentiiied p application result: in may be substltuted if desired with other substltuents, a cured system having outstanding properties, including 222 2 35253252? sg g gi g They may also be hi h bend stren th at room tern erature to ether with 6%) hi h strengih at elevated ter riperature g Th6 .monomencitype pqlyepoiude Compounds l be The E of the co pending pp (with exempllfied bythe followlngz vmyl cyclohexene dioxide, crence to carbohydrazide) may be set forth briefly as Sai flfig gggf g si ggg g f follows: the carbohydrazide and epoxy resin are made (7 OX r0 g ag 18 (2 3 homogeneous, as by stirring, and heated so as to partially J P i 5 r0 advance the system to a predetermined terminal vis- 25 g fl g i diglyciayletger p yp p y cosit The s stem is then cooled at a controllable rate, and, at some liter time (e.g. a minute a week or months) other polymenc polyepoxlde compounds i the the system is employed in a particular assembly or appolymers and.cop0]ymerS of the EPOXY'CPmammg plication 6% as a coating and finally cured in situ e}? possessing at least one polymcrlzable ethylenlc i.e. on the articular material of the assembl or a plication. The resulting cured product has Zutstan Another groul? polyepoxldesl mc-ludes the epoxy ing physical Properties over the nonmdvanced or com esters of polybaslc acids, such as dlglycldyl pthalate and ventionany cured material dlglycrdyl adlpate, diglycldyl tetrahydrophthalate, dl-

Comparative results are set forth below in Table I. ifi i alfld h The gel time is that time remaining before the resin my pm rre p0 ycijoxl as are t e mqno' system gels. The resin mixture not advanced was heated i and polymimc-type glycidyl pplyethers i at 300 F for 40 minutes in contact with a metal strip dnq pile-Hols obtalped by reacnng eplchlorohydrm to be theta) cured a dlhydrlc phenol 1n an alkaline medlum. The monomer y TABLE I products of this type may be represented by the general 40 formula:

P.h.r. Ad- Gel on b 1 Adtl R.T. 300F. R.T. Resin vanced V5133? (s35 shear shear bend CHWCH GET-O R O GHQ-CH CH2 3 32 g p 356?]? wherein R represents a divalent hydrocarbon radical 0f the dihydric phenol.

The amounts of carbohydrazide can range between 113 Y ng??? in $25 212 35 58 ,3 83 and 40 per hundred parts epoxlde resin, although optlrnum results are usually obtained when employing from 1 equals parts per hundred ofresm, between 8 to 20 parts per hundred parts epoxide resin. R.T. equals room temperature. To further illustrate the manner in which the inven- In contrast with the above increase in physical prop- 110K} y he earned out, the following example is herties, when dihydrazides are cured with the epoxide It 15 t0 he 1mder$00 f that the f p 15 resins, by means of our novel partial advancement procthe P p as were the P P ess, no increase in physical properties of the finally cured amPles, and the lnvtfntlon 15 hot to be regafdhfl as hmlffld material takes place. This is indicative of the apparent to of lhfi speclfic COmPOUHdS COIldltIOIlS reclted different reactions that carbohydrazide and the dihydra- 'thefelnzides may undergo, and the inability to predict, in adhulldffid Parts Of p xyn e mvfed vance, the properties of a particular curing agent-epoxy W11 24 parts Of carbohydrazlde, y sh m a reactwn resin system. The actual comparative data for 3 dis t EP XY-H VOIaC reSm used belng One of the hydrazides are set forth in Table II. 0 X2638 series of resins manufactured by Dow Chemical TABLE II Advance- Gel R.T. Resin Curing agent P.h.r. Adment time P.s.t. at P.s.l.nt bend,

vanced te ufip. RT. 300 F lbs.

Epon 828-- Isophthnllc dihydrazide 2, 990 2,460 132 o 2, 520 2, 800 121 Do Sebacicdlhydrazide 3,825 865 112 130.--. 2,995 890 158 130.-.- 1,865 710 90 Do 2,190 610 as The epoxide resins or polymers which are operative Company. (The specific epoxy-novolac resin used was in my invention are known commercial materials and X26383.) The epox-novolac resins are based on poly.

functional phenols of the phenol type rather than being based on the bisphenol-A type of epoxide resin.

The resin mixture was stable below temperatures of 40 F. The mixture was then poured onto a metal strip, heated in situ for 15 minutes at 275 F., and for 40 minutes at 310 F. The resin composition was, at this point, completely cured, and possessed extremely good salt spray resistance.

Iclaim:

1. A new composition of matter comprising an epoxide resin having a 1,2 epoxy equivalency greater than 1.0, produced by the reaction of a polyhydric phenol with a 1,2-epoXy-3-halohydrin, and 6 to 40 parts per hundred, by weight, of said resin, of carbohydrazide.

2. The composition of claim 1 wherein 8 to 20 parts of carbohydrazide per hundred parts of resin are used.

3. The reaction product obtained by reacting 100 parts of an epoxide resin having a 1,2 epoxy equivalency greater than 1.0, produced by the reaction of a polyhydric phenol with a 1,2-epoxy-3-halohydrin, with 6 to 40 parts per hundred, by weight, of said resin, of carbohydrazide.

4. The reaction product of claim 3 wherein said reaction takes place at about 300 F.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Grant: Hackhs Chemical Dictionary, page 167, third edition, 1944. 

1. A NEW COMPOSITION OF MATTER COMPRISING AN EPOXIDE RESIN HAVING A 1,2 EPOXY EQUIVALENCY GREATER THAN 1.0, PRODUCED BY THE REACTION OF A POLYHYDRIC PHENOL WITH A 1,2-EPOXY-3-HALOHYDRIN, AND 6 TO 40 PARTS PER HUNDRED, BY WEIGHT, OF SAID RESIN, A CARBOHYDRAZIDE. 